(April 25, 2002)
There are three types of amphibians: 1) Frogs (Anura), 2) Salamanders (Caudata), and 3) Caecilians (Gymnophiona).
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Species Numbers
The largest genus of frogs is also the largest genus of all vertebrates, yet it is relatively unknown to the general public. This is Eleutherodactylus, known generally as the "rain frogs" or the "tink frogs". There are more than 500 species, with more being described each year (get the latest number by querying the AmphibiaWeb database). These frogs occur throughout the New World tropics, and species extend into Florida, Texas and Arizona. The best known species is Eleutherodactylus coqui, the living symbol of Puerto Rico, where its characteristic call can be found over the entire island. This species has been introduced into Hawaii, where it is considered a pest because of its ubuitous call.
The largest genus of salamanders, with more than 80 species (get the latest number by querying the AmphibiaWeb database), is Bolitoglossa (the "web-footed salamanders"), which ranges from Mexico throughout Middle America and most of South America to central Bolivia. These are fully terrestrial salamanders that lack an aquatic larval stage and frequently are arboreal in habits. The best known species is probably Bolitoglossa pesrubra, which is common in the highlands of Costa Rica where it has been seen by many biologists taking the classes of the Organization for Tropical Biology.
The largest genus of caecilians, with more than 30 species, is Ichthyophis, which ranges throughout much of southeastern Asia, including many of the Phillipine, Malasian and Indonesian islands. These organisms are rarely seen unless one searches specifically for them.
The "typical" life cycle of amphibians is a larval stage that lasts a few months, followed by brief metamorphic period, then a long, multiyear life on land. The adults return to the water to court and ultimately lay eggs. However, there are many exceptions. Among frogs the very large genus Eleutherodactylus lays its eggs on land and they develop directly into miniatures of adults with no tadpole stage. These are the most widespread and commonly encountered frogs in the New World tropics. In Africa the genus Arthroleptis (known as "squeakers") are all direct developers. There are also many other direct developing frogs on Madagascar and in southeast Asia. Among salamanders most species of the largest family, the Plethodontidea, are direct developers. There are also direct developing caecilians.
A few species of frogs give birth to living young. Members of the African genus Nectophrynoides retain eggs in the oviduct and some nourish the young as they grow. These are born as miniatures of the adult. One Puerto Rican species of the genus Eleutherodctylus, now thought to be extinct (E. jasperi), also retained eggs in the oviduct and had live birth. Salamandra salamandra, S. atra and some related species either give birth larvae or to completely metamorphosed juveniles. Many species of caecilians give birth to living young, usually fully metamorphosed at birth.
Salamander escape!
Hydromantes platycephalus, the Mount Lyell Salamander, lives under rocks on talus slopes. When the rock is lifted up, the salamanders curl into a ball and roll away down the hillside away from potential predators.
Parental care
Strawberry Poison Dart Frogs, Dendrobates pumilio, avoid laying their eggs in ponds and streams. Instead, the eggs develop on land until the tadpoles are ready to hatch. Then the mother carries the tadpoles on her back to water-filled bromeliads (epiphytic plants) in the trees. The tadpoles complete their development in these tiny, predator-free pools, and the mother feeds them with unfertilized eggs.
Males of Rhinoderma darwinii, Darwin’s Frog, brood their developing young in their vocal sacs until they metamorphose. Female Gastric-brooding frogs, Rheobatrachus silus, brood the developing young in their stomachs. They do not feed at all through the developmental period, and can have over 20 young.
Live-bearing caecilians provide nutrition to their developing embryos. The young have well developed jaws and teeth which they use to scrape secretions, called “uterine milk,” from the walls of the oviducts.
The biggest, the smallest, the highest....
The largest amphibian in the world is the Chinese Giant Salamander Andrias davidianus purported to be up to 180 cm from the nose to the tip of the tial. An animal that was 115 cm long weighed 25 lbs!
The largest frog is the Goliath Frog Conraua goliath
The largest caecilian is Caecilia thompsoni which reaches 151.5 cm; the smallest is Grandisonia brevis at 11.2 cm but a female of Idiocranium russeli was gravid at 90 mm.
The smallest salamander is probably Thorius arboreus The smallest salamander is one of several species of the genus Thorius that achieve sexual maturity at about 15 mm snout to vent length. Thorius arboreus from the Sierra de Juarez of Oaxaca is the smallest species, because the largest known adult is a female (the larger of the two sexes in this genus) that was only 20.0 mm snout-vent length (Hanken and Wake, Copeia, 1998).
The smallest frog is probably from the genus Eleutherodactylus. One of the smallest recorded Eleutherodactylus is about 10 mm long (snout vent). There are several very small frogs, right about 10 mm sv, including Psyllophryne didactyla from Brazil and Stumpffia (S. tridactyla for example) from Madagascar. It is difficult to know what the smallest frog is as there are many very small species.
The highest elevation amphibian is....?
The salamander that goes to the highest elevation is Psuedoeurycea gadovii which goes above 5000 meters on Volcan Orizaba in Mexico.
What is the highest elevation frog?
There is some controversy on this topic. It may be Bufo latastii. It was described as Bufo siachinensis by Khan in 1997 who reported that it was from 5238 m in the Karakoram of Pakistan -- a truly high frog! Borkin (in Duellman, 1999) said this "seems to be the world record of the highest distribution of a species of amphibian". However a recent paper by Stöck et al. (2001) points out that the latitude is at least 15' off. Furthermore the two specimens, supposedly from the end of a glacier, were given by another person to Khan. Shinu Village, which is said to be "close" to the type locality, is below 4000 m. In South America (Peru), a frog in the genus Telmatobius gets close to or above 5,000 m.
So, what is the highest living amphibian?
Lots of amphibians reach 4000 m but only very few frogs and salamanders go much higher. Caecilians generally are below 1500 m.
How long do they live? A Salamandra salamandra lived for 50 years in captivity, and an Andrias japonicus lived for 55 years. An Ambystoma maculatum in nature was estimated from skeletochronology to be 27 years old. A Bufo bufo lived 36 years in captivity (Duellman and Trueb, 1986).
WHAT DO YOU CALL A GROUP OF FROGS?
A herd of elephants;
A flock of birds;
A ______ of frogs?
(Answer: chorus)
What do frogs have in their mouths that toads don't?
Teeth. Most frogs have teeth on the upper jaw but none on the lower jaw (only one frog has teeth on the lower jaw -- an unusual species from South America). The word "toad" is an informal name applied to the large frog family Bufonidae, and these animals all lack teeth entirely (along with some frogs in other families).
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